Circulating plasma volume and renal function

Area of Science:

• Nephrology
• Physiology
• Cardiovascular Research

Background:

• Circulating plasma volume (PV) influences renal function, including glomerular filtration rate (GFR) and effective renal plasma flow.
• Understanding these relationships is crucial, especially in conditions like chronic glomerulonephritis.

Purpose of the Study:

• To investigate the relationship between plasma volume and GFR/effective renal plasma flow.
• To examine how upright posture affects these parameters in healthy subjects and patients with chronic glomerulonephritis.

Main Methods:

• Investigated changes in GFR and effective renal plasma flow in response to changes in PV induced by upright posture.
• Compared these relationships in normal subjects and patients with chronic glomerulonephritis.
• Analyzed the correlation between changes in mean arterial pressure and GFR.

Main Results:

• A consistent power function relationship was observed between percentage changes in GFR and percentage changes in PV (GFR = k * PV), with no significant difference between normal subjects (k=3.4) and patients (k=3.1).
• Effective renal plasma flow changes showed a biphasic relationship with PV.
• Changes in mean arterial pressure did not correlate with GFR changes.

Conclusions:

• GFR is regulated by a power function of plasma volume, particularly during decreases in PV, rather than by mean arterial pressure.
• The findings highlight the critical role of plasma volume in maintaining renal function.
• Potential mechanisms involving the renal arterial system structure are considered.